1. Field of the Invention
This invention relates to a video data processing device and a video data processing method that can suitably be used for a recording/reproduction apparatus adapted to compression-coding input video data and recording them on an optical disc.
2. Related Background Art
Compression-coding conforming to the MPEG (Moving Picture Experts Group) Standard is known. With compression-coding conforming to the MPEG Standard, the amount of video data to be handled is reduced by utilizing spatial correlations of data in a same frame and temporal correlations of data in different frames.
Therefore, the recording/reproduction apparatus using a coding system conforming to the MPEG Standard compression-codes the input video data to generate compression-coded video data and record them on an optical disc. For data reproduction, the recording/reproduction apparatus reproduces the compression-coded data from the optical disc and expansion-decodes the data to restore the original video data. In this way, the recording/reproduction apparatus can efficiently records a vast amount of video data on the optical disc by suing a coding system conforming to the MPEG Standard.
Some of the recording/reproduction apparatus of the above described type are adapted to always output a predetermined volume of compression-coded data by adaptively filtering the video data to be compression-coded before the compression-coding operation. More specifically, of the frames of the video data to be compression-coded, those that show a weak temporal correlation are subjected to an operation of reducing the high frequency component of the frame before the compression-coding process whereas those that show a strong temporal correlation are compression-coded without being subjected to a reduction of the high frequency component.
Thus, with such a recording/reproduction apparatus, if the volume of compression-coded video data is expected to increase because the temporal inter-frame correlation is low, the volume of information of the high frequency component is reduced before compression-coding the video data so as to always output a predetermined volume of compression-coded data because the image quality is not remarkably degraded to the sight of the viewer if the volume of the high frequency component of information is reduced.
However, if the image compression rate is raised, the volume of the high frequency component can be reduced to such an extent that the degradation of the sharpness of the reproduced image is recognizable to the sight of the viewer. The operation of reducing the volume of the high frequency component is conducted in the coding preprocessing step or in the coding processing step. Then, an operation of compensating the reduced volume of the high frequency component is conducted after the decoding processing step.
However, when the video data to be compression-coded is adaptively filtering before the compression-coding operation, the degree of filtering can vary depending on the image to be filtered. Therefore, if the operation of compensating the reduced volume of the high frequency component is conducted uniformly after the decoding processing step, some of the images to be compensated can be compensated inadequately.